Is it legal for a county government to halt all subdivisions?

Our county has denied every major subdivision over the last 8 months because of faulty road rules. They are currently getting sued by several developers because the county was forcing developers of new subdivisions to pay more money in off-site road improvements leading up to the subdivision than the total money the development would have made. Now the county has just stopped approving subdivsions, unless the developer agrees to paying for all the road upgrades. Is it me or is this a form of extortion. Their goal has been to make developers foot the bill for building all road upgrades in the county instead of using taxpayer dollars to provide the necessary improvements. And recently the county just changed their road standards making every road in the county out of standard, thus allowing the county the power to make a developer upgrade as many miles of roads as they choose. The tool the county has been using is safety.